When the U.S. Defense Advanced Research Projects Agency (Darpa) declared its intent to make close air support more responsive by enabling ground forces to directly control the weapons on unmanned aircraft, it raised a few eyebrows. When it revealed a heavily armed Fairchild A-10 would be converted to optionally piloted operation for the Precision Close Air Support (PCAS) technology demonstration, eyebrows arched even higher.

Now the skeptics can relax, somewhat, as the PCAS program has been reshaped to focus on near-term transition of the technology to manned close-air-support (CAS) aircraft. An A-10 will still be used as the testbed for live-fire trials, but will be flown manned. And PCAS will still demonstrate that a joint terminal attack controller (JTAC) on the ground can directly control the weapons on an aircraft, but the outcome will not lead to automated, unmanned CAS.

Instead, the product of the demonstration will be hardware and software that provides improved communications and shared situational awareness between the JTAC and the pilot, and autonomous decision aids that recommend actions to increase the speed and accuracy of CAS.

Raytheon is moving ahead to demonstrate more rapid and precise close air support after finalizing a contract with Darpa for Phase 2 of the PCAS program. “The fundamental goal is still the same: to decrease the timeline by a factor of 10 from a request for fire to an effect on target from 60 min. to 6 min. for an A-10 loitering 20 nm away,” says Dave Bossert, Raytheon program manager. “And we will still use the A-10, but not optionally manned.”

The modified program comprises two elements. PCAS-Air is the airborne system, providing the interface between the aircraft, its sensors, weapons and pilot, and the JTAC on the ground. PCAS-Ground is the kit carried by the JTAC, including an Android tablet computer, head-up display and digital radio.

PCAS will provide improved communications between JTAC and pilot, with all-digital messaging and shared displays of sensor imagery, targets, weapons and their effects. “The PCAS-Air piece was the A-10. Now it is 'Smart Rail' electronics, small enough so that anything that can carry the Hellfire missile can be PCAS-Air-enabled,” Bossert says, adding “We are platform-agnostic, sensor-agnostic and radio-agnostic.”

The Smart Rail includes a computer that hosts the PCAS algorithms, a GPS/inertial navigation system and talks to the JTAC via a dedicated data-link radio and to the aircraft, sensors and weapons via an interface box. An Android tablet identical to that carried by the JTAC is mounted in the cockpit for the pilot.

“Tight coupling of the JTAC and pilot is key,” Bossert says. PCAS provides the JTAC access to the computing power and high-resolution sensors on the aircraft without the Smart Rail having to be part of its operational flight program. “It is separate from, but hosted on, the aircraft,” he says, which will reduce the time/cost for adding PCAS capability.

Raytheon's modified $12.9 million Phase 2 contract will culminate in a critical design review in November, and Bossert says there is a “high probability” Darpa will proceed into the 18-month, $25.5 million Phase 3 flight demonstration. Team members include GE Aviation providing its stores and payload controller and Rockwell Collins supplying high-bandwidth QNT radios, head-mounted display systems, and targeting and visualization tools.

The program changes reflect a shift in focus for near-term transition of PCAS to manned CAS, from unmanned. “One of the original sponsors when we started was the MQ-X [unmanned aircraft] program. There is no MQ-X anymore,” he says. MQ-X was the U.S. Air Force's planned Predator/Reaper replacement, but never got beyond concept studies.

“The primary focus was never the optionally piloted A-10, and it became somewhat distracting,” Bossert says. Instead of enabling the JTAC to directly control weapons on an aircraft, PCAS is most likely to transition to operational use as an autonomous decision aid for the pilot. “Manned CAS has the biggest need,” he says.

“It will be part of their situational-awareness decision aids, showing recommended actions for both the pilot and JTAC,” Bossert continues. “For the PCAS demo, we still plan autonomous weapons employment, but a pilot will fly the A-10 and be able to override the autonomy.”

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